Single mode (SM) fiber, with it's virtually unlimited bandwidth, has become the telecommunications standard despite the precise alignment tolerances and corresponding high components costs. However, the alignment tolerances for multimode (MM) fiber is typically a factor of 10 or more looser than for SM fiber. Unfortunately, the standard 62.5 micron core MM fiber has a limited bandwidth-distance product of typically 160 and 600 MHz-km. This means that a 10 GHz signal would degrade unacceptably after transmission over a distance of 16 to 60 meters.
An optical switch array (also referred to herein as an optical cross connect [OXC] or optical crossbar) is used to provide switchable cross connects between optical fibers. One prior art optical crossbar, illustratively shown in FIG. 1, is described in U.S. Pat. No. 5,524,153 issued on Jun. 4, 1996 to the Astarte company. This optical crossbar provides an array of free-space optical connections between collimated input and output fibers. With reference to FIG. 1, this system enables an input fiber, e.g., 101, to be selectively switched to any output fiber, e.g., 110. The switching is accomplished using a piezo-electric lateral actuator (not shown) which laterally translates, 102, the input fiber 101, relative to the axis of a collimation lens, e.g., 103, thereby enabling the optical beam, 104, to be steered or directed to the collimation lens, e.g., 105, where another piezo-electric actuator has translated, 111, fiber 110 into the correct location to receive optical beam 104.
Undesirably, these prior art optical crossbars (OXC) have required beam steering units at each of the input and output fibers. Beside being costly, the physical size of these beam steering units affect the overall size of the optical crossbar. With the continued emphasis on cost reduction and miniaturization, what is desired is an optical crossbar that is lower cost and smaller.